Garda Commissioner Martin Callinan has resigned after weeks of battling allegations of wrongdoing in his ranks.

The Irish police chief said he was stepping down in the best interests of his family following intense pressure to withdraw controversial remarks about two whistleblowers.

"I felt that recent developments were proving to be a distraction from the important work that is carried out by An Garda Síochána on a daily basis for the citizens of the state in an independent and impartial manner," Mr Callinan said in a statement.

He was thought to have issued his resignation "with immediate effect" to Justice Minister Alan Shatter.

Whistleblowers Maurice McCabe and John Wilson raised concerns that well-connected motorists were having their driving penalty points cancelled by garda.

Sinn Féin justice spokesman Pádraig Mac Lochlainn, who chairs parliament's public service oversight committee, said Mr Callinan was right to quit.

"From the moment that the allegations from the two garda whistleblowers emerged about widespread malpractice of the penalty points issue the commissioner sought to downplay and even dismiss the allegations," he said.

"Worse, he repeatedly sought to discredit the credibility of the two whistleblowers which culminated in the outrageous 'disgusting' comment at the public accounts committee."

Mr Mac Lochlainn said two recent reports by both the comptroller and auditor general and the garda inspectorate vindicated the whistleblowers' core allegations.

Mr Shatter tweaked retirement rules last year to allow the commissioner to stay on past 60, allowing Mr Callinan to oversee deep spending cuts demanded by Ireland's internationally imposed bailout deal.

But the financial woes - which included the closure of 100 police stations - were the least of his worries as the garda faced a series of high-profile allegations of wrongdoing.

The long-running Smithwick inquiry reported last year that "loyalty is prized over honesty" in the garda, concluding that officers colluded in the murders of two Royal Ulster Constabulary officers in 1989.

And last May the ombudsman Gsoc accused the force of withholding vital evidence from its inquiry into allegations that elite officers colluded with a convicted drug trafficker.